Initial experience with a novel Ultra-Low-Temperature Cryoablation System for ventricular tachycardia ablation – The CryoVT study

Background: The effectiveness of radiofrequency (RF) ablation of ventricular tachycardia (VT) is limited by the depth of RF lesions beyond endocardial and subendocardial layers. A novel ultra-low-temperature cryoablation system (ULTC) which uses "near-critical" nitrogen refrigerant near its boiling temperature of -196°C may provide increased tissue depth and scar penetration and thus improved outcomes for VT ablation.

Aim: The aim of this study was to evaluate the safety and efficacy of a novel ULTC system in patients undergoing catheter ablation of ventricular tachycardia (VT) or premature ventricular contractions (PVC).

Methods: All consecutive patients undergoing de novo or repeat catheter ablation of either VT or PVC with the use of ULTC were prospectively enrolled at a tertiary ablation center between April and June 2024. Patient characteristics, acute procedural data, as well as safety and efficacy are reported.

Results: ULTC was performed in eight patients (age 63.6 ± 9.5 years, 100% male, ejection fraction 36 ± 12%). Most patients had underlying ischemic cardiomyopathy (75%) with the rest having non-ischemic cardiomyopathy. Six patients had an ICD implanted prior to the ablation. Four patients had undergone at least one previous VT ablation, one patient had undergone VT ablation followed by a stereotactic radiation therapy for VT recurrence and was admitted again with electrical storm. PVC ablation was attempted in two patients, VT ablation in the remaining six patients. All ablations were performed under deep sedation and electroanatomical guidance with a high-density mapping catheter using the Biosense-Webster Carto system in one and the Abbott Ensite NavX system in seven cases. Preprocedural transthoracic echocardiography or cardiac magnetic resonance imaging (MRI) was used to assess the depth of the target tissue and titrate cryoenergy according to an available ULTC titration protocol. A bonus freeze protocol (bonus freeze after each freeze at each location) was used in all patients. Substrate mapping and substrate-based ablation was the most common approach utilized in 87.5% of the patients. Mean procedure duration was 120.5 ± 28.1 min, with a mean freeze duration of 28.7 ± 9.1 minutes, a mean minimum freeze temperature of -155.63 ± 15.4 °C. The lowest freeze temperature reached was -174 °C. A total of 1.9 ± 1.1 VTs with an average cycle length of 328 ± 94 ms were induced in six patients, of which 37.5% were deemed to be the target clinical VT. The acute endpoint of freedom from any re-induced VT was achieved in five of the six VT patients. No minor or major complications were observed. During short-term follow-up no sustained VT or ICD interventions occurred. The mean PVC burden was reduced from 18 ± 1% to 3 ±2%.

Conclusion: In this first commercial application, endocardial ULTC ablation for either VT and/or PVCs appears to demonstrate potential safety and efficacy in both ischemic and non-ischemic cardiomyopathy. Additional research is necessary to thoroughly investigate both acute and long-term safety outcomes associated with this innovative ablation technology.

Figure 1        Ultra-low-temperature cryoablation in patient number 4. Left and middle: Ensite NavX substrate map illustrating the posterior substrate with the cryo ablation point in red and the ULTC catheter in grey (left). Right: Fluoroscopy with the ULTC catheter during ablation via an antegrade approach.